Austin PC. Some methods of propensity-score matching had superior performance to others：results of an empirical investigation and Monte Carlo simulations[J].Biomet J，2009，51:17l-184．
[8]
Flury BK,Reidwyl H.Standard distance in univariate and multivariate analysis[J].Am Statistician,1986,40:249-251．
[9]
Austin PC.A critical appraisal of propensity-score matching in the medical literature between 1996 and 2003[J].Stat Med，2008,27：2037-2049.
[10]
Austin PC,Grootendorst P,Anderson GM.A comparison of the abilitv of different propensity score models to balance measured variables between treated and untreated subjects：a Monte Carlo study[J].Stat Med,2007,26:734-753．
